Search results for "sampling"
showing 10 items of 788 documents
Dealing with the Pseudo-Replication Problem in Longitudinal Data from Posidonia Oceanica Surveys: Modeling Dependence vs. Subsampling
2012
Posidonia oceanica represents the key species of the most important ecosystem in subtidal habitats of the Mediterranean Sea. Being sensitive to changes in the environment, it is considered a crucial indicator of the quality of coastal marine waters. A peculiarity of P. oceanica is the presence of reiterative modules characterizing its growth, which lend themselves to back-dating techniques, allowing for the reconstruction of past history of growth variables (annual rhizome elongation and diameter, primary production, etc.). Such back-dating techniques provide, for each sampled shoot, a longitudinal series of multivariate data; this is an instance of what Hurlbert (1984) in a seminal paper d…
Suppression law of quantum states in a 3D photonic fast Fourier transform chip
2015
The identification of phenomena able to pinpoint quantum interference is attracting large interest. Indeed, a generalization of the Hong–Ou–Mandel effect valid for any number of photons and optical modes would represent an important leap ahead both from a fundamental perspective and for practical applications, such as certification of photonic quantum devices, whose computational speedup is expected to depend critically on multi-particle interference. Quantum distinctive features have been predicted for many particles injected into multimode interferometers implementing the Fourier transform over the optical modes. Here we develop a scalable approach for the implementation of the fast Fouri…
Population genetic analysis of bi-allelic structural variants from low-coverage sequence data with an expectation-maximization algorithm
2014
Background Population genetics and association studies usually rely on a set of known variable sites that are then genotyped in subsequent samples, because it is easier to genotype than to discover the variation. This is also true for structural variation detected from sequence data. However, the genotypes at known variable sites can only be inferred with uncertainty from low coverage data. Thus, statistical approaches that infer genotype likelihoods, test hypotheses, and estimate population parameters without requiring accurate genotypes are becoming popular. Unfortunately, the current implementations of these methods are intended to analyse only single nucleotide and short indel variation…
The uncertainties of climate change in Spanish daily newspapers: Content analysis of press coverage from 2000 to 2010
2014
This paper explores media coverage of climate science through a selection of Spanish newspapers (El País, El Mundo, ABC, Expansión and Levante). We selected a stratified random sample of 363 items to be studied for eleven years (2000-2010). Content analysis allowed us to find out media attention paid to climate science, prevalence of informative tables, evaluation and characterization of news, as well as the presence of questioning or rejection of climate change. According to main results, press coverage of climate science in Spain was mainly focused on the consequences rather than on the causes or natural sources, and media attention paid to it was limited. Overlapping with social and macr…
A flux retrieval error behavior with CERES/TRMM data
2003
With the aid of CERES/TRMM (Clouds and the Earth's Radiant Energy System/Tropical Rainfall Measuring Mission) data, sampling problems that may impact the construction of anisotropic models have been investigated. We show the influence of the sun-orbit geometry, which causes a lack of measurements in forward and backward scattering directions at large viewing zenith angles, and how cloud properties retrieval algorithms as obtained from the Visible Infrared Scanner (VIRS) also affect sampling. We have also focused our attention on the dependency of the cloud cover retrieval algorithm with respect to the viewing zenith angle (VZA), showing that the shape of the cloud cover probability density …
Sensitivity of the C-band SRTM DEM Vertical Accuracy to Terrain Characteristics and Spatial Resolution
2008
This work reports the results of a careful regional analysis of the SRTM DEM (Shuttle Radar Topography Mission – Digital Elevation Model) vertical accuracy as a function of both topography and Land-Use/Land Cover (LULC). Absolute vertical errors appear LULC-dependent, with some values greater than the stated accuracy of the SRTM dataset, mostly over forested areas. The results show that the structure of the errors is well modeled by a cosine power n of the local incidence angle (θloc). SRTM quality is further assessed using slope and topographical similarity indexes. The results show a lower relative accuracy on slope with a R2 = 0.5 and a moderate agreement (Kappa ≈ 0.4) between SRTM- and …
Intrasite Artefact Survey at Terravecchia di Cuti (Sicily)
2016
In this paper, we discuss the results of an artefact survey and a sampling collection in the indigenous settlement of Terravecchia di Cuti, in the chora of the Greek colony of Himera (Sicily). The whole area of the town was gridded with squares of 10x10 m to isolate functional areas and identify the most interesting zones for new archaeological samples. The survey was carried out in two fields (9400 m2), counting and recording all findings. Only diagnostic pottery and figured pottery, antefixes, loom weights, millstones and so on were collected. We can observe, analysing in detail our results for both fields, that functional areas could not be isolated, perhaps because the urban and social …
Assessment of the Geochemical Potential in a Complex Tectonic Environment of South-East Sicily: New Insights From Hydrochemical Data
2019
We analyzed a large dataset (143 water sampling sites, 22 variables) of chemical parameters in local groundwaters from the south-east sector of Sicily, namely the Hyblean plateau, in order to set an original evaluation of its geothermal potential using applied geochemistry. The area was affected by volcanism until about 1.4 Ma. Today, though no active volcanism occurs, it is site of surface gas manifestations of focused degassing to which a mantle source has been attributed. We identified and thence selected the most promising sites (water springs and wells) based both on their main geochemical characteristics and on their calculated equilibrium temperature (resulting in the range between 5…
Self-reported chronic mental health problems and mental health service use in Spain.
2009
Objectives: To determine the prevalence of self-reported chronic mental health problems (MHPs) and mental health service use and their determinants, among the Spanish population over 14 years of age. Methods: Data from the 1999 Spanish Survey on Disabilities, Deficiencies, and State of Health were used. The survey is a cross-sectional study based on a multi-stage stratified sample of all the non-institutionalized Spanish population aged over 14 years (n=59,101, 11% non-responders). Multivariate logistic regression analysis were used. Results: 10.7% of the Spanish population suffer from an MHP. The highest prevalences were found in women, divorced/separated persons, those with a lower level…
Regular exercise history as a predictor of exercise in community-dwelling older Japanese people
2012
A physically active lifestyle is important across the entire life span. However, little is known about life-long participation in regular exercise among older people. The purpose of the present study was to describe regular exercise throughout a person's lifetime and evaluate the impact of exercise earlier in life on participation in exercise at age 60 and over. The participants were 984 community-dwelling older people aged 60 to 86 years. Each participant's life was divided into five age categories: 12-19, 20-29, 30-39, 40-59, and 60 years and over. The association between exercise at an earlier age and that at 60 years and over was assessed using logistic regression analysis adj…